A liquid crystal display has been used lately as the display of various electronic devices. A liquid crystal display device includes two substrates and a liquid crystal layer interposed between the two substrates and conducts a display operation by regulating the voltage applied to the liquid crystal layer on a pixel-by-pixel basis so as to vary the orientation states of the liquid crystal layer.
It is known that a liquid crystal display device may have some display non-uniformity due to a variation in the thickness of the liquid crystal layer (which is also called a “cell thickness”), which is one of major problems with liquid crystal display devices. The cell thickness is usually defined by photo-spacers. However, as those photo-spacers finished may have various sizes, the cell thickness may be non-uniform within the plane of the display screen, which in turn produces a distribution of retardations (i.e., the phase differences caused by the liquid crystal layer on the incoming light) within that plane, thus generating such display non-uniformity.
FIG. 13 shows the voltage-transmittance characteristics of a liquid crystal display device with varying cell thicknesses. In FIG. 13, shown are a curve representing a voltage-transmittance characteristic in a region with a normal cell thickness (of 3.0 μm, specifically) and a curve representing a voltage-transmittance characteristic in a region with a cell thickness that is smaller than the normal value by 0.3 μm. In such a region with the smaller cell thickness, the retardations are also relatively small. That is why as can be seen from FIG. 13, the voltage-transmittance curve in the region with the smaller cell thickness is less steep than the voltage-transmittance curve in the region with the normal cell thickness. That is to say, when compared at the same applied voltage, the region with the smaller cell thickness has a lower transmittance than the region with the normal cell thickness. Consequently, the region with the smaller cell thickness will be sensed as a region with the lower brightness (i.e., a darker region) on the display screen. On the other hand, a region with a greater cell thickness than the normal one will be sensed as a yellowish region with the higher brightness (i.e., a brighter region) on the display screen.